Process of making soluble coffee concentrate



Aug. 14, 1956 PROCESS OF MAKING SOLUBLE COFFEE CONCENTRATE F. A. CHASE YFiled Feb. 18, 1955 CURVE j PREFERRED FHA/6E g 5X fg ZZ 40 *y* 55X Mgg:i

2 4 e 10 12 14 Je x Hou/RS INVENTOR. Waff/2er A7. (Mae m JW UnitedStates Patent O PROCESS F MAmG SLUBL'E COFFEE CONCENTRA'I'E Fletcher A.Chase, Morris Plains, N. J., assiguor, by

mesne assignments, to American Home Products Corporation, New York, N.Y., a corporah'on of Delaware Application February 18, 1953i, Serial No.337,523 2 Claims. (Cl. 99-71) This invention relates to an improvedsolid soluble coffee concentrate and a process of making it in whichground raw coee is extracted, the extract evaporated, and the extractresidue roasted.

In making all the commercially successful solid coffee concentrates nowon the market, ground roasted coffee is extracted with water by one oranother of available processes and the extract evaporated to dryness.Many variations of these steps have been developed in an effort toimprove avor and aroma, to increase yield and to introduce economiesinto the process. None has been entirely satisfactory in all respects.During all extractions of roasted coffee there is a significant loss offlavor and aroma and a further loss of avor land aroma during drymg.

Early in this development the thought was advanced that loss of aromaduring extraction and evaporation of the extract might be avoided byextracting green coee instead of roasted coee, evaporating the extractbefore the development of the aromatic constituents in volatileV form,and finally roasting the solid residue resulting from the evaporation todevelop avor and aroma. This concept appears fundamentally sound, butapparently insuperable diiiiculties have hitherto been encountered inits practical realization.

One of the early workers in this field was Von Vietinghoff. In U. S.Patent 1,175,091 issued to him in 1916 for a diierent method ofpreparing a soluble solid coffee extract, he detailed reasons for thefailure of what I call for short the raw-bean process, i. e. broadly,the process in which the beans are extracted before roasting. vVonVietinghoff said, the practical diliiculties encountered make theprocess inoperable. These diiculties were: (1) that some of thesubstances dissolved from the raw beans become insoluble on roasting thesolid evaporated extract, thus leaving a residue when coiee beverage ismade from the extract; (2) ditculty is encountered in evaporating theextract of the raw beans due to foaming and high viscosity owing to itscontent of albumen; (3) diiculty is encountered in roasting theresulting extract in an approximately homogeneous manner.

Later L. G. Copes and associates attacked the problem by introducingmodifications into the step of extracting the raw beans. In U. S. Patent1,932,769, issued in 1933, Copes, Haurand and Kellogg disclose a processin which insoluble materials (apparently those referred to by VonVietingholf) are eliminated by preheating the green coffee, or anextract thereof, to a suitable temperature, considerably lower than thetemperature to wbich'cofree is ordinarily roasted. According to thesepatentees, for example, ground green coffee may be boiled in water longenough to make the deleterious materials insoluble, the extract filteredand evaporated, and the residue roasted. Or, alternatively, the groundgreen coee may be extracted at a lower temperature and the extractboiled,

2,758,927 Patented Aug. 14, 1956 filtered, and worked up. Or the groundbe steamed before extraction.

In U. S. Patent 1,933,049, also issued in 1933, Copes discloses amodified process in which ground green coffee is mixed with twice itsweight of cold waterl and allowed to stand for twelve hours, after whichthe liquid is pressed out. The solid residue is then treated withboiling water for about l0 minutes and the liquid pressed out; this stepmay be repeated. The hot and cold extracts are united and evaporated todryness, either under vacuum or atmospheric pressure, and the residueroasted.

Neither of these processes produces a solid soluble coffee concentrateof a quality to satisfy the present highly educated public taste, andneither has, as far as l know, been successfully exploited commercially.

green coffee may It is one object of my invention to produce a solidsoluble colee concentrate of superior taste and aroma.`

It is another object of my invention to produce a residue ofgreen-coffee extract that may be convertedto such a concentrate byroasting.

It is a further object of my invention to provide a process for theabove purposes that is economical and that may be carried out for themost part in conventional equipment.

Other purposes and advantages of my invention Willbe apparent to thoseskilled in disclosure.

I have discovered that when ground green colee is subjected to alow-temperature extraction, the low-temperature extract is extremelyunstable and immediately shows signs of decomposition, apparently due toenzymes extracted from the green coffee. Such low-temperatureextraction, however, is necessary to obtain the aromayieldingconstituents of the coffee. A high-temperature extraction mayadvantageously supplement the low-temperature extraction to obtain aneconomical yield from the coffee beans and to impart body to the avor ofthe final product. However, the high-temperature extraction, whiledesirable for producing an optimum product complete in itself, is notessential, especially when the product is to be blended with aconventional solid soluble coifee concentrate to impart improved aromaand avor. I have found that my process, as disclosed andrclaimed below,produces a product of exceptionally high quality and utility, and thatin its practice the diiiculties encountered in prior processes aresubstantially eliminated.

According to one embodiment of my process, therefore, I rst extract theground raw coffee beans at a relatively low temperature and evaporatethe extract under such conditions as to avoid the above mentioneddecomposition, which is very deleterious to the quality of the finalproduct, and then extract the thus partially extracted raw coffee at ahigher temperature. Finally I evaporate the extracts to dryness androast the residue, producing a solid soluble concentrate which, alone orblended with conventional concentrates, produces a superior beveragewhen dissolved in water.

Prior to extraction, the raw beans are ground. The size of the granulesis not critical, but I have had good results by grinding to such aneness that passes a 3 mm. screen and 75% is retained `by a 0.5 mm.screen.

The low-temperature extraction may be carried out at a'wide range oftemperatures-e. g. 60-2l2 P but I prefer to work in the range 60-100 F.The extraction may be carried out by agitatng the ground raw coffee withwater at the desired temperature, or by circulating water at the desiredtemperature through a mass of vthe ground raw coffee, or by making thelow-temperature extraction the last stage in a continuous multi-stagecountercurrent process in which hot water is brought'into Contact withnearly exhausted coifeein the iirs`t.stage and leaves the the art fromthe following.

urne, may be usedz instead of water.I

system at a loriI temperature after contact with fresh unextracted' rawcoffee. The low-temperature extraction may even be carried out in wholeor in part by grinding the raw coffee in the presence of walter. Inallthese exltraction modincations, dilute ethanol, up to 50% by vol-There is thus a wide range of conditions under which this phase of myprocess can be operated.

in hours rThere is, however, .a critical limitation in'carryingdeleterious decomposition of the extract. I lllaveround and immediatelyafter `completing the extraction. Altercessary to and is less in thelabsence ofrair, e. g. under av blanket or este wifi' aise referirdeierieieiien.

xy-43x-0.3y=260 (l) of x being not over 16 and those of y being in therange physical law, but represents pr tical Working 4lil'nt's with 200F. thev extraction should not last more than 2v hours ever., be carriedout in shor'te'r times than these and in The extract, if not evaporatedimmediately, may be sible. Under an atmosphere of inert gas, such VasCO2 for 16 hours may range as high-as 75 F;

diate evaporation to ensure consistent production of mateobserved.

batch or continuous extraction, should preferably be ditions. Iifspecial precautions to inhibit deterioration extraer fiiey .be eterea a'eeneiderebiy 16s-ger time witte-ui temperatur"' may be expressed byhyperbolic equations tions do not have the precision f establishedphysical and y the storage temperatnre in degrees F., tiie preout' the.low-temperature extraction and evaporation, conditioned by' the need ofavoiding the abovementioued that be Yavoided (a)` by limi-ting theAduration of theextriaction, and (n) by evaporating the extract rapidlynatively li), ne delay they evaporation, tlvie extract rnay be lstored alirnited'time without serious deterioration byrefrigerating to AaY lowtemperature,`vi"z. 32,-50 F. Deterioration is slower at lowtemperatures,

iiieft gee eueii es co2 er N2.I Tiie addition ef eiit'ioxi- Tiiedurationofmthe low-temperature extraction step -at various temperatures,within which the advantages of invention'imay berealized, may beexpressed empirically by a hyp erb`olic equation iii whieii x representsine duration in nears ein y the temperature of the extraction in egreesF., the values 60-212. l Owing -to the natural variation properties ofconce, this equa-tion does not have the preision of a a reasonabledegree of approximation; Curve 1 in the drawing illustrates the'equation. It will be seenl that at and at 100 F., not more than 5 hours;at 60 F., 16 hours should not be exceeded; Extraction can, how'- generalbetter quality is secured with extractions of lesser duration than theseniax'ir'ria.

stored for as long as 16 hours at 40 F. without serious deterioration,4but this storage is to be avoided if posor N2; `or the addition of aneffective non-toxicantioxidant .s'uch a's tocophf'zr-ols,` theterriperatiire of storage This storage period is as critical as or evenmore critical than the extraction peri'od. Best practie requiresimmerial o f optimum quality. Nevertheless highly satisfactory productsmay be 4obtained if certain precautions are The time betweeneempiet'ieii er exfreiie 'and evepe'- nation of a' low-temperatr'eentract, whether from a not'longer 2 hours at- 70 F. andiii any case notmuch longer than 4 hours at 70 F., under ordinary oon-v are observed,such a's storage ofthe extract in an inert atmosphere or with addednon-toxic antioxidant, the

becoming unusable;

The relation of permissible times of storage to storage with .closeapproximation, but,- as pointed out above,- in view of the naturalvariability of naw yeiee tlies 'ed-daf laws.

If x represents the storage time ferred limits are given by the equation@essie-poneros However, by observing the following conditions in theabsenee of special precautions to avoid decomposition,

reasonably good results may be obtained. If the extract is stored underan inert gas or if a non-toxic antioxidant is `added inaneiectiveamount, storage time may be extended as indicated by' theequation In ne essie is storage advisable for more .their 16 iris.

Equation' 2 is represented lby curve' 2 the dnawiirg, Equation 3 bycurve 3', and Equation 4 by curve 4;

The deterioration of the low-temperature extract which occurs if theabove on'ditions are not observed, appears to be, in part at least, anenzymatic fermentation, and its onset is usually characterized byincipient effervescence. y

The High-temperature extraction of 4my process, when employed, may becarried out in a' range or temperatures from 212 F. up to about 300 F.or somewhat' above, e. ig. toV 325 F. This extraction is preferablyapplied to the partiallyl extracted coffee' resulting ifro'ni' the lowtemperature stage, but in one modification of my riven# .tion it may beapplied yto fresh ground raw coffee. In either case the extract is4further worked up as described below.

While various types and lots or coffee yield diierent amounts of solidconcentrate under like conditions, the following table' shows how yieldstrompa representative coffee vary with the temperature in thehigh-temperature stage in my invention. The percentage gures representtotal yield of solid concentrate from typical extractions, based on theweight of green coffee used.

TABLE Gage pressure, Yield from lb. per sq. in. green beau,

l Charring.

In -botli stages of batch extretion, the eiitract' may be separated fromthe grounds by vacuum, pressure iiltra` tion, gravity filtration or `bypressing tlie grounds. In general I prefer pressure ltratiori, as in alter press or tient'rifuge. In 'a continuous counterc'rrent extraction,such as that mentioned above, pressure filtration or pressing of theexhausted grounds is usually unneessar'y, since the small amount ofliquor remaining in tle exhausted grounds at the high-temperature orentrance end of the system isY not rich Venough to warrant recovery.

After each extraction is complete I evaporate tlie extract to drynessasA promptly and rapidly as practicable. In the' ycase of -batchextractions, I prefer to evaporate the lowand hi lit-temperatureextracts separately. Since,

however, the high-temperature extract is :less liable to" deleteriousdecomposition than the low-temperature ex' tract, the highatemperature'extract of one batch may be stored until the low-temperature extractionof a second batch is completed, and the two extracts blended beforeevaporation;

in the continuous countercurrent extraction mentioned above, only oneextract is produced, since cooled hightemperature extract is used forthe low-temperature extraction o fresh green coiee at the exitend of thesysf teni, and this contains the' entire solubles yield of the eofieetreated. is evaporated preferably rapidly en@ ai once after thecompletion of iiie'extraeiicn, or alter-natively'with the precautionsoutlined above to avoid dele-` terious decomposition, e. g.refrigeration.

As pointed out above, in the low-temperature extraction step in therange 60 212 F. the contact of green coffee and extract should not belonger than 2 hours in the upper part of the range and may be longer inthe lower part of the range. In a continuous countercurrent system inwhich the extraction is carried out in a series of closed percolatorssubstantially free of air and in which the temperature drops from say,around 300 F., at the end where water comes into Contact with nearlyexhausted coffee, to 60 F. at the end where extract leaves fresh rawcoffee, vthe time of Contact will be the same in each percolator if thepercolators have a uniform cross-section, as is usually the case.Accordingly the duration of contact will be controlled by the cold endof the train where conditions similar to those applicable to batchevaporation must be observed. The sensitivity of the extract todecomposition increases in passing through the train as its temperaturedrops below 212 F. and as it comes into contact with fresher and fresher(i. e. less extracted) raw coffee. The relations are somewhatcomplicated here by the additional variable, the degree of exhaustion ofthe coffee in the different stages, but in general it is preferable notto exceed a time of 2 hours in each percolator.

The evapora-tion of the extracts, whether separate or combined, may becarried out in numerous ways, the chief requirement being avoidance ofexposure of the extract to high temperatures for an extended time. Whilesome types of vacuum evaporation are feasible, I prefer to use either aspray drier, in which the time of evaporation may be less than l second,or an external -atmospheric drum drier in which the time of drying maybe a few seconds.

The residues of evaporation of the lowand high-temperature extracts arefree flowing granular powders having va greenish or brownish cast with acharacteristic green coffee odor and taste, and a moisture content ofless than 3%. Using the preferred meth-od of drying, i. e. spray drying,a product of uniform particles is obtained which lends itself to uniformroasting. This material is further treated to prepare a solubleconcentrate suitable for making beverage coffee by roasting. Conditionssimilar to -those used in conventional coffee roasting may be employed.Because, however, of the nature of the material, optimum roasting timesand temperatures will vary much more with variations in conditions thanis the case with coffee beans. Among such Variable conditions are:amount of material, depth of layer, method of heating, air circulationand the like. With small amounts of material, without forced aircirculation, good results have been obtained, for example, withtemperatures in the neighborhood of 410 F. for 15-17 minutes.

When the evaporation residues of my invention are roasted, they gothrough a plastic stage and at the same time they foam; as the roastingproceeds, the material solidilies but retains its foam structure. Theresult is that the roasted product is a friable porous mass which may bereadily pulverized. This roasted product is completely soluble in coldor hot water and in proper concentration yields a beverage having allthe attributes of a beverage freshly brewed from fresh roasted coffee.

Examples of embodiments of my process follow. They are intended to beillustrative only, and not to limit my invention, the scope of which isdefined in the appended claims.

Example I Raw coffee beans are ground to a fineness such that 100%passes a 3 mm. screen and 75% is retained by a 0.5 mm. screen.

200 pounds of ground raw coffee is placed in a covered jacketed kettleprovided with an agitator and 100 gallons of water introduced at atemperature of 200 F. The air in the kettle is displaced with CO2 andthe contents of the kettle are slowly agitated for 11/2 hours, whilethe'tem-eY The ltrate is then immediately spray-dried to a mois-l turecontent of approximately 21/2 The filter cake is transferred again tothe kettle, the; kettle charged with hot water, and the contentsraised'to about 300 F. or slightly higher, but not over 325 F. Air isbled from the kettle so that the extraction takes place under a blanketof steam at about 60-100 lb. per sq. in gage pressure. The extraction iscontinued for 1 hour with slow agitation, after which the contents ofthe kettle are discharged ately spray-dried.

The combined residues of the spray-drying operations are thoroughlymixed, spread in thin layers on trays and roasted in an -oven with aircirculation for 15-17 minutes at 390 -410 F. The porous friable darkbrown product is comminuted to suitable size and packaged. 'For longtermstorage it may be packaged under vacuum or in an atmosphere of CO2 orN2.

Example 2 One hundred pounds of green coffee 'beans and 400 pounds water(48 gallons) at 70 F. are fed into a mill,` lsuch as a Fitzpatrick mill,operating at 7000 R. P. M. and having a 1%6 round mesh screen, andground to a fine pulp. There is little or no temperature rise. The pulpis centrifuged, a filtrate being obtained containing coffee solublesamounting to approximately 30% of the weight of the green coffee. Thisfiltrate is then spray-dried at an inlet air temperature of 500 F. andan outlet tem-Y perature of 240 F. to a moisture content of 21/z%, thedrying being nearly instantaneous. The resulting residue is roasted andground to a uniform particle size. Dissolved in water, this productproduced a beverage of fine aroma and full bodied coffee flavor.

Example 3 Twenty parts by weight of the solid soluble concentrateproduced in Example 2 is homogeneously mixed with 80 parts by weight ofa high-grade commercial soluble coffee concentrate made by thehigh-temperature extraction of roasted coffee. The two products arecompatible, and the aroma and flavor are superior to that of thecommercial product alone.

Example 4 Water under pressure at a temperature of 285 F. is pumped intoone end of a train of nine percolators connected in series. Thepercolator at the outlet or cool end cf the train contains a charge of1000 pounds of highgrade fresh ground raw coffee and the otherpercolators contain corresponding amounts of coffee progressivelydepleted in solubles towards the inlet or hot end. The water is pumpedthrough the train at the rate of 320 gallons per hour. The temperaturein the three percolators at the hot end is maintained at about 285 F. bymeans of heat exchangers between the percolators, and the temperatureIof the extract as it passes through the other percolators to the outletend is lowered gradually to 70 F.

The train is operated on a 11/2 hour cycle. After 11/2 hours ofcirculation, i. e. after 480 gallons (4000 pounds) of water has passedthrough the train, the coffee in the percolator at the hot end isexhausted; that percolator is cut out of the train and emptied whilesimultaneously a percolator charged with fresh ground raw coffee isshunted in at the cold end of the train. A train of 9 percolators incircuit and two standby percolators (one for charging and one forcleaning and servicing) can be operated indefinitely by repetition ofthis cycle. This process thus constitutes a continuous countercurrentextraction process in which continuously more depleted and filtered. Thefiltrate is immedicoiee ifs' moved stepwise againstA a stream of extractof continuously increasing concentration.

larger or smaller num'ber -of percolators may' be used, and the design,piping' connections, and' installation of auxiliary equipment may bevaried widely,- aswill be well understood by those familiar with thisart.

The effluent from the cold endv ofthe trin is run into a receiving tankat a temperature of approximately' 70 F. From the tank it is run to aspray-drier (first through a clarifying lter if necessary) and rapidlydried to a tine uniform-greenish brown powder containing less than 3%moisture. The receiving tank represents a safety factor to provide forpossible lack of coordination of extractiontrain and spray-drieroperation. Under normal operating conditions the euent will remain inthe tank an exceedingly sho-rt time, or the tank may be by-'passedentirely. In any case, storage in the tank at '70-75 F. should notexceed 2 hours.

The powder from the spray above,- ground and packaged. l

The products of my invention are solid soluble coffee concentrateswhich, dissolved in water in an amount to suit the individual taste,furnish a coffee beverage lof superior body and aroma, closelyduplicating a coffee beverage properly brewed in the conventional wayfrom freshly roasted and ground high-grade coffee. As will be"understood from this disclosure by those skilled in the art', rnyinvention comprises variations and modifications within the' scope ofthe' following claims.

1. ri a process of preparing aA soluble solid coiee extract byextracting un'roasted coffee with an aqueous medium at not above 212 F.,separating and spraydrying the extract, and roasting the residue at acoifeeroasting temperature, the improvement which comprises:

drier is roasted as disclosed carrying ont the extraction whilesin'lu'ltaneous'lyy grindl ing the unroasted coee in the extraetivemedium,-fsep, ara'ting and spray-drying the extract and. roastingy theresidue at a coffee-roasting temperature,- limiting thetime andtemperature' of simuitaneous extraction and grinding to: 2 to 16` hou-rsat 212 to 60 F. and limi-ting the time and temperature of holding theseparated extract before. drying to 0 to 16 hours at 212 to 40 F., thelongertimes being for the lower' temperatures and the shorter times forthe higher temperatures, wherebyA deleterious decomposition of the greenextract is avoided.

2'. ln a process of preparing a soluble solid colfee ex; trac-t byextracting ground unroasted coffee at not above 212- F.1,- separatingand spray-drying the extract., and; roasting the residue at acoffee-roasting temperature, the improvement which comprises: utilizingas the extracting medium for the groundnnroasted coitee at not abiQYe-212 F. an extract obtained by extracting partially exhausted groundcoffee with water in the temperature ran-ge 212-32-5 E., limiting thetime and temperature of extraction at not above 212 F.l to 2- to 16hours at 212 to 60" Ff, and limiting the time and temperature of holding`the separated extract before drying to O to 16 hours at- 212 to 40 F.,the longer times being for the lower temperatures andthe shorter timesfor the higher temperatures, wherebyk deleterious decomposition of thegreen extract is avoided.

References Cited in the file of this patent UNTTED STATES PATENTS1,932,769 Copes et al. Oct. 31, 1933 1,933,049 Copes Oct.4 31, 1933l2,149,876 Wendt et al.A Mar. 7, 1939 2,515,730 Ornfelt July 18, 1950

1. IN A PROESS OF PREPARING A SOLUBLE SOLID COFFEE EXTRACT BY EXTRACTINGUNROASTED COFFEE WITH AN AQUEOUS MEDIUM AT NOT ABOVE 212* F., SEPARATINGAND SPRAYDRYING THE EXRACT, AND ROASTING THE RESIDUE AT A COFFEEROASTINGTEMPERATURE, THE IMPROVEMENT WHICH COMPRISES: CARRYING OUT THEEXTRACTION WHILE SIMULTANEOUSLY GRINDING THE UNROASTED COFFEE IN THEEXTRACT AND ROASTING THE RESIDUE AT A COFFEE-ROASTING TEMPERATURELIMITING THE TIME RESIDUE AT A COFFEE-ROASTING TEMPERATURE, LIMITING THETIME AND TEMPERATURE OF SIMULTANEOUS EXTRACTION AND GRINDING TO 2 TO 16HOURS AT 212* TO 60* F. AND LIMITING THE TIME AND TEMPERATURE OF HOLDINGTHE SEPARATED EXTRACT BEFORE DYRING TO 0 TO 16 HOURS AT 212* TO 40* F.,THE LONGER TIMES BEING FOR THE LOWER TEMPERATURES AND THE SHORTER TIMESFOR THE HIGHER TEMPERATURES, WHEREBY DELETERIOUS DECOMPOSITION OF THEGREEN EXTRACT IS AVOIDED.